The Impact of Tectonic Activity on the Morphology of Longitudinal Profiles of the River Case Study: Polrood River (North of Iran)

The longitudinal profile of the rivers provides valuable information about the changes in the conditions governing the catchment areas. For this reason, it has always been the favorable subject of many researchers. By examining the longitudinal profiles of the rivers, we can examine the status of tectonic activities in the region. In this research, the longitudinal profile of the catchment area of ​​ Polrood river basin and its effective factors were investigated. In order to do this research, the study area is divided into 10 basins and sub basins, and in each of these basins, the sub-basins, type of flow, the amount of tectonic activity and exit points of equilibrium status in the form of longitudinal profile of the river were identified. In the tectonic assessment of the under study river basins and sub-basins, some of the active tectonic indicators of Hi, the SL index and also the drawing of the Ds diagram have been used.Also, the results obtained from calculating the hypsometric integral indices and the SL index in these basina and sub basins indicate the mild rate of tectonic and uplift activity. The formation of NIC points and fractures in the Basin and sub-basins of Plourod, Shelman and Jirkol are litho logical changes. In other words, litho logical changes in these three basins and sub-basins cause distortion of the longitudinal profile of the river. The rate of hypsometric integral in the basin of the Polrood, Shelman and Jirkol basins is 0.79, 0.59 and 0.38, respectively. These values ​​indicate a relatively high level of tectonic activity in these three basins, however, litho logical changes in these basins and sub-basins are the cause of forming fractures and imbalance in the longitudinal profile of the river. Values of hypsometric integral ​​in Selechal, Asgharabad, Chalakrood and Sorkh-Ghele sub-basins are 0.54, 0.6, 0.45 and 0.44, respectively, which indicate the mild tectonic level in the sub-basins of the Chalakrood And Sorkh-Ghele, as well as relatively high tectonic rates in the sub-basins of Asgharad and Selechal. The cause of imbalance and fracture in the longitudinal profile of the river in this basin and sub-basin is a combination of tectonic and litho logic factors. The highest rate of SL index anomalies is in sub-basins of Selechal, Asgharabad, Chalakrood, which are high and resistant in terms of litho logy, the remaining anomalies of basins and sub-basins of the study area have values of SL index of medium up to low. Eventually, the study carried out in this basin and the obtained results, it was revealed that the shape of the longitudinal profile of the Polrood River is more subject to litho logical changes and tectonic processes have less effect on it.